Quartz oscillator plate



March 16, 1948. c. FROIQDEYL 2,431,915

QUARTZ OSCILLATOR PLATE Filed Dec. 5, rem

l ENTOR 7 RD FRONDEL ATTORNEYS Patented Mar. 16, h

UNITED STATES PATENT OFFICE- QUARTZ OSCI'LLATOR PLATE Clifiord Frondel, Flushing, N. Y., assignor m Reeves-Ely Laboratories, Inc., New York, N. Y., a corporation of New York Application December 15, 1944, Serial No. 568,329

16 Claims. (Cl. 171-327) 1 This invention relates to quartz oscillator have been and are being developed in the oscilplates and has for its object certain improve later-plate industry. Thus, in the sd-called acidments in the method of manufacturing oscillator dip or etching process, the plates as obtained at plates made of quartz Or equivalent material. the completion of the machine lapping are In the manufacture of so-called BT quartz os- 5 brought up to the desired frequency by dipping cillator plates, for example, automatic or semithem for the required length of time into a solautomatic machines are generally employed in the vent for quartz. This solvent, which may be, for initial and intermediate states. The final finishexample, hydrofluoric acid, removes quartz from ing of the plates is, however, still largely a hand the surface of the plate and thus acts to reduce operation, the work being done by highly skilled the thickness of the plate to the desired value. operatives, usually called finishers. In finishing This process, as with hand lapping, requires an the plates, physical dimensions of the order of intermittent, successive, series of treatments and sub-millionths of an inch are involved. The film measurements, especially in the final stages, to isher is usually provided with a frequency-checkensure that the desired frequency is exactly ating device, a flat glass. plate, fine abrasive, an tained. The rate of etching of different plates of etching solution, water, a brush, cleaning solut e S e al frequency s not t a due tions, lint-free towels, a micrometer, an optical to variations in the cleanliness of the surface, fiat, a small square, etc. the roughness of the surface, and other factors,

The finisher receives the plates, sometimes so that a uniform, timed, procedure for all plates called blanks, asthey come from mechanical lappcannot be set out. In still another method of ing machines, the plates having been cut to subfinishing plates the desired cy. the stantially proper length and width and usually plates are tumbled with an amount of course brought close to, but less than, the desired osabrasive in a container until the frequency cillating' frequency. In a plate desired to have proaches that desired. The plates are then rea final frequency of, say, 8000 kc., the machine moved, cleaned, and are adjusted to the desired lapping or other pre-hand-finishing treatment frequency either by etching or hand lapping.

is stopped when the plate is from roughly a few Alternate hand lappin cleaning and testing hundred cycles up to ten or more kilocyeles are required until the plate reaches the desired under the final desired frequency; Apreliminary qu n T a v t of e p at s d t rfrequency check is then made by comparing the mined by its di C p l is a frequency of the plate with that of a standard 581108 f flaws. eleanness. vThese p ys c l plate having a known frequency. This gives the characteristics are checked, changed, d finisher a general idea how much hand lapping checked until the desired activity is obtained. the plate should be given. To reduce the plate The frequency of the P at changes with chan to its proper thickness, and hence to increase made to the plate to obtain the desired activity. its frequency, the finisher grinds the plate in a so that the finisher must coordinate the numerous mixture of the abrasive and water on the fiat variables going into the finishing operation to glass plate,- keeping the faces of the plate as fiat obtain a combination of conditions that yields and parallel as possible. The plate is next thora plate of predetermined activity and frequency. oughly cleaned and dried, after which its fre- 40 Hand finishing by these methods of the oscilquency is again tested. This is done by insertlator plates is a tedious, slow, delicate and costly ing the carefully cleaned plate in a holder, plugoperation at best and leaves much to be desired. ging the holder intoan oscillator circuit and not.- The human factor is an exceedingly important ing whether or not the plate has reached the element in these finishing operations and the redesired oscillating frequency. The lapping of sults obtained tend naturally to vary from person the major plane surfaces of the plates usuallyto person, depending'upon the particular techis accompanied by a lapping or beveling of the nique employed at the time by each finisher.

edges of the plates; this operation,by removing As a result of my investigation I have discovroughness and other imperfections from the ered that the frequency and certain other charedges and by altering the edge dimensions, gives acteristics of piezo-electric bodies may be adjustthe desired degree of activity, so-called, to the ed or varied without altering the physical dimenplate. sions of the body, such as by grinding, etching The finishing of a plate to its desired frequency or plating with a metal or other material. The also may be accomplished in other ways, and a frequency of oscillation of quartz oscillator plates, number of techniques other than hand lapping for example, may be varied continuously and this ping the treatment at the desired value or within the desired range. This is not possible in present methods of manufacture of piezo-electric bodies which, as noted above, involve a discontinuous alternating process of grinding or etching, cleaning and testing. The frequency of oscillation of quartz oscillator plates may, for example, be readil adjusted to a desired value with an accuracy up to 1 cycle or greater, depending primarily on the accuracy of the measuring device employed. This accuracy cannot be accomplished by the conventional method of grinding or etching because the amount of grinding or etching on which the change of frequency and accuracy depends cannot be accurately controlled or measured, and the change in frequency itself cannot be observed continuously.

The frequency of a piezo-electric body that has been put into a relatively stable state by means of baking, sulfuric acid washing of other treatment, such as for the purpose of eliminating or reducing spontaneous variation with time in the frequency or activity of the piezo-electric body,

lator plates are subjected to the action of high speed deuterons in amount sufllcient to decrease their frequency of oscillation.

A deuteron is a singly charged composite particle consisting of a proton and a neutron bound together tightly but not inseparably. It has about twice the mass of a single proton; the neutron ls uncharged, and is slightly heavier than the-proton. Deuterons are comparable to alpha particles of the same velocity in their ionizing action, The behavior of the oscillator plates under deuteron bombardment is identical with that under irradiation with X-rays and radium radiawhich a. deuteron particle falls, the greater the kinetic energy it acquires. High voltage generacan be adjusted withoutdestroying the stability of the piezo-electric body. This is not possible by present methods of manufacture. For example, if a number of quartz oscillator plates are brought by grinding or etching to a desired frequency, and are then baked or otherwise treated, for the purpose of stabilization, it is found that the frequency often changes erratically from the original value and must then be adjusted by additional grinding or etching. This action then destroys the stability of the oscillator plate and the purpose of the original stabilizing operation is lost, This readjustment can now be accomplished without grinding or etching and without loss of stability.

The frequency of oscillator plates may be adjusted, for example, without wetting them with water or other liquids and in an entirely dry condition. Water is commonly used in the conventional method of finishing to frequency by lapping with an abrasive or by etching, and has been considered to contribute substantially to undesirable ageing and other phenomena in the finished oscillator be obviated.

The frequency of a piezo-electric body can be adjusted while it is contained in its permanent holder, whether this is of the contact (pressure), air gap, wire suspension or other type of mount. If desired, the frequency of the piezo-electric body may be adjusted before it is mounted in its permanent holder.

The change in frequency brought about by application of the invention is downwards from the initial value, but the downwards change may be reversed, and the frequency restored to its original value, by suitable treatment. The new technique is especially advantageous in the recovery of oscillator plates that have been overshot by the ordinary methods of hand finishing. Oscillator plates that have increased in frequency over the upper tolerance due to ageing, or aged low activity plates that have gone over the tolerance after cleaning to bring up the activity, may be similarly readjusted to their original frequency.

In accordance with the invention, quartz oscilplate. This difficulty may now tors may be used to accelerate deuterons along suitably constructed tubes and, at the end of their journey, the quartz oscillator plates may be bombarded with them. It is much more feasible, however, to use a cyclotron, in which the deuterons at regular intervals are given a succession of relatively low voltage pushes until they acquire the speed equivalent to that obtained when a high voltage is employed.

To reduce the frequency of the oscillator plates, they are placed in the path of a stream of high speed deuterons as they emerge from the window of the cyclotron. The oscillator plates may be placed in the circuit of a frequency meter, so that the change taking place may be visually observed and the treatment terminated when the oscillator plates have reached a. predetermined frequency, or at least fall within a predetermined frequency range.

The change in frequency produced in oscillator plates by the high speed deuterons is downwards from the original value. The change is progressive and continues during bombardment but finally reaches a limiting value determined by factors within the quartz beyond which there is no further change. The rate of change appears to depend primarily on the speed of the deuterons at the time they strike the quartz oscillator plates, but in part on variations in the properties of the quartz from specimen to 'specimen and on pre-treatment of the quartz. The continuity of the change is of great importance from a manufacturing point of view. The downward direction of the change is also of particular advantage.

The downward change in frequency brought about by the high speed deuterons is permanent under ordinary conditions but can be reversed and the oscillator plate brought back to its original frequency by baking at a suitably elevated temperature or by irradiating the plate with ultra violet rays. Ultra-violet rays reverse the action of the high speed deuterons. The ability to reverse the downward change is of great advantage. In other words, the oscillator plates may be adjusted downwards and upwards in frequency repeatedly by the proper treatment.

The rate at which the downward change in frequency of the oscillator plates can be efiected by the high speed deuterons and the total amount of change is influenced by the temperature at which the plates is held during bombardment and by previously baking the places at a suitably elevated temperature.

These and other features of the invention will be better understood by referring to the accompanying drawing, taken in conjunction with the following description, in which:

tation in cross-section, taken on the line 2-2 of Fig. 1; and

Fig. 3 is a similar diagrammatic plan representation showing a quartz oscillator plate mounted in a holder connected to a frequency meter.

Referring first to Fig. 1, the apparatus shown comprises a juxtaposed pair of Ds l0 and II. in the form of 'hollow semi-circular boxes, which lie in the region between the pole pieces of a powerful magnet, not shown. The Ds are also provided with means, not shown, for applying alternating voltages. D m has a bulging portion l2 so as to provide a window 13 through which the high -speed deuterons may emerge. The window is, in turn, covered with a window pane of sheet steel sufficiently strong to withstand atmospheric pressures when Ds In and II are evacuated. A quartz oscillator plate It is shown in front of the window, the plate being held on a sliding holder l6 movable in an upper track I! and a lower track l8 by means of a handle l9.

Referring next to Fig. 2, the apparatus shown comprises a similar pair of Ds with a quartz oscillator plate M located in front of window l3 of D H]. In this case, however, the oscillator plate is mounted in a holder 25 of conventional construction. The casing of and the electrode within the holder around the oscillator plate are shown broken away for convenience. The holder is, in turn, connected with a frequency meter 26 by means of a pair of leads 2! and 28. The frequency meter may be of conventional 'designl, having a needle 29 adapted to move back and forth over a graduated frequency scale 30, preferably divided to indicate cycles per second.

When operating the apparatus shown, the air is first exhausted from Ds l0 and II. A little heavy hydrogen isthen passed into the Ds at their centers and is ionized by a suitable device, not shown, to produce deuterons. The value of the magnetic field and the frequency of the oscillating electric circuit are so chosen that during the time of a reversal of voltage between Ds l0 and II, the deuteron to be speededup moves through exactly half a circle.

When, for example, a deuteron D is released at the center of the Ds and a semi-circular region to the right thereof in D II is impressed with a voltage so directed as'to speed up the deuteron, it and other deuteron particles in that region will possess kinetic energy of an equivalent number of electron-volts. In addition, a strong magnetic field is maintained at right angles to the plane of the Ds, the magnetic lines of force M likewise exerting a force on the deuteron particles. Deuteron particle D is moved outwardly from the center of the Ds by the impressed voltage and is then made to move in an are by the magnetic field. The resultant force causes the deuteron particle to move in a semicircle, as indicated by the arrows.

At the end of its first half circle, the voltage is alternated and the deuteron particle moves over into D H), where it is given an additional push and made to continue in a semi-circle course. By the use of rapidly alternating voltages, which are maintained between two conductors by means of high frequency circuits, the

deuteron particle receives a push after the completion of each half circle, thus making it go faster in the next half circle. The paths of the deuteron particle continue to widen because of the increase in speed each half circle. The path of the deuteron particle is a spiral composed of these half circles, each a little greater than the one before it.

When employing one of the larger cyclotrons, the deuteron particle receives literally hundreds of pushes, thus causing the deuteron particle to make hundreds of revolutions, the speed being picked up on each successive push so that by the time the deuteron particle has made a spiral path toward the outer perimeter walls of Ds l0 and II, it has attained a tremendous speed and, an enormous amount of kinetic energy. The speed and kinetic energy are sufficient for the deuteron particle to pass through the window pane of steel in window l3 and to be bombarded against quartz oscillator plate l4. A great multitude of such deuteron particles are started on their whirling spiral journey and emerge from the window to strike the oscillator plate. The effect of the high speed deuterons on. the oscillator plate is gradually to decrease its frequency of oscillation. The bombardment of the oscillator plate with the high speed deuterons may be conducted until the oscillating characteristics of the oscillator plate fall within a predetermined range or reach a predetermined value.

When using apparatus such as that disclosed in Fig. 2, the predetermined frequency range or value may be noted visually on frequency meter- 26. When needle 29 is deflected until it pointsat the desired frequency. or frequency range indicated by scale 30, the oscillator plate' is taken out of the stream of high speed deuterons or the stream of high speed deuterons is shut off.

With a deuteron beam or stream at 14 M electron-volts and 20 microamperes, the oscillator plates underwent a decrease in frequency in some instances amounting to over a kilocycle in an exposure time of a few minutes.

The rate of change of frequency during irradiation is rapid, at first, but drops off with time and distance, finally to approach a limiting value. The magnitude of the limiting value varies with different specimens of quartz. This variation, which in the extreme cases so far encountered is about tenfold, appears to depend primarily on a predisposing feature in the quartz itself. The actual rate of change in frequency in a given oscillator plate varies with the conditions of treatment, and primarily with the intensity of radiation. The decrease in frequency during irradiation is accomplished with little, if any, significant change in activity.

As previously noted, the frequency of quartz oscillator plates also undergoes a change when the plates are treated with ultra-violet rays; the change in frequency, however, being upwardly insteadof downwardly. Oscillator plates irradiated as described above in order to decrease their frequency may be reverted in frequency to their by the other'type of radiation disclosed. its fresuch as gold, silver, aluminum or an alloy which may serve the purpose of making a better or more intimate electrical contact with or act as electrodes; or which may serve as Protective or stabilizing films. The plates may, for example, be coated with amorphous silica or organic plastic or other material which may serve the purpose of protective or stabilizing films. In the case of oscillator plates that have been protected or stabilized by a plating, coating or other treatment, including heating and ageing, the radiations herein contemplated are adapted nevertheless to modify the oscillator plates so as to vary their oscillating characteristics; and irradiation of the plates may be conducted until their frequency of oscillation reaches the desired value without substantial loss of stability. The plates may be adjusted upwards or downwards in frequency repeatedly by use of the proper radiations.

It also is possible to adjust the plate to have a desired frequency at a given temperature by irradiating the plate,'and bringing it to frequency, while it is held at that temperature in a suitable heating or cooling contrivance. This is not easily accomplished by the conventional lapping or etching techniques of finishing plates.

The rate of change of frequency of the plate during irradiation and also the total amount of frequency change that can be obtained (saturation value) can be modified by baking the quartz plate at a suitable temperature before it is irradiated. Thus, the quartz plate may be sensitized to frequency change by heating it to a suitably elevated temperature, for example up to 570 C. This substantially increases both the rate of change and the amountv of change of frequency over that which would obtain if the plate had not been baked beforehand.

The oscillator plates may be irradiated whether mounted or unmounted. It is advantageous to irradiate the plates while they are mounted in a temporary or permanent holder and while the plates are oscillating. It is particularly advantageous to conduct the irradiation operation while the oscillator plates are mounted in a permanent holder connected with a suitable meter. so that the change in frequency of oscillation which takes place may be visually observed and the irradiation stopped when the plates have attained the desired frequency. The type of permanent holder, for example, may be of the pressure or clamp, air-gap, combined pressure and air-gap, wiresupport, mechanically or hermetically sealed,

temperature-controlled or temperature-protected,

or the multiple-type. If the oscillator plates are mounted in a permanent holder, the radiations go right through the plastic, glass or metal shell or housing of the holder. A sufllciently penetrating radiation must, of course, be employed. This practice is especially useful in the case of oscillator plates supported between wire suspension mounts in thin-walled vacuum holders. If the 7 mined 8 oscillator plates are not mounted in a holder. they may be held, for example, in paper or aluminum foil envelopes which protect them from moisture, dust and grease spots from handling.

It also is convenient under certain circumstances to irradiate a large number of plates simultaneously. This can be done, for example, by stacking the plates together and placing the stack directly in front of the window, face on. The amount of frequency change thus brought about is not uniform through the stack, but is greatest in the first plate, considerably less in the second, and then decreases more slowly in succeeding plates.

While the practice of the invention has been described with respect to piezo-electric material in the form of quartz, it will also be clear to those skilled in this art that the inventionis applicable to the treatment of other piezo-electric materials, such as Rochelle salt, tourmaline, tartrates, etc. The invention is applicable to the treatment of any useful piezo-electric material the frequency and oscillating characteristics of which are to be varied under controlled conditions.

I claim:

1. In the-manufacture of quartz oscillator barding each oscillator plate with high speed deuterons adapted to decrease its frequency of oscillation, and terminating the treatment of the plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value. v

3. In the manufacture of quartz oscillator plates, the improvement which comprises bombarding each oscillator plate while mounted in a holder connected to a frequency meter with high speed deuterons adapted to decrease the frequency of oscillation of the plate, and terminating the treatment of the plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value.

4. In the manufacture of quartz oscillator plates, the improvement which comprises bombardlng each plate while mounted in a holder connected to a frequency meter to the action of high speed deuterons adapted to passthrough the housing of the holder and to decrease the frequency of oscillation of the plate, and terminating the treatment of the plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value.

5. In the manufacture of quartz oscillator plates, the improvement which comprises bombarding each plate while maintained at a predetermined temperature with high speed deuterons adapted to decrease its frequency of oscillation. and terminating the treatment of the plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value.

6. In the manufacture of quartz oscillator plates, the improvement which comprises maintaining each oscillator plate at a predetermined temperature while mounted in a holder connected to a frequency meter, bombarding the plate while at said temperature with high speed deuterons adapted to decrease the frequency of oscillation of the plate, and terminating the treatment of the plate with said high speed deuterons when its frequency of oscillation reaches a predetervalue.

'1. In the manufacture of quartz oscillator plates, the improvement which comprises maintaining each oscillator plate at a predetermined temperature while mounted in a holder connected to a'frequency meter, bombardingthe plate to the action of high speed deuterons adapted to pass through the housing of theholder and to decrease the frequency of oscillation of the plate, and terminating the treatment of the cooled plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value.

. 8. In the manufacture of quartz oscillator plates, the improvement which comprises grinding each oscillator plate to a thickness beyond that required to increase its frequency to a predetermined value, and bombarding the ground plate with high speed deuterons adapted to decrease its frequency of oscillation.

9. In the manufacture of quartz oscillator plates, the improvement which comprises grinding each oscillator plate to a thickness beyond that required to increase its frequency to a predetermined value. bombarding the ground plate with high speed deuterons adapted to decrease its frequency of. oscillation, and terminating the treatment of each ground plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value.

10. In the manufacture of quartz oscillator plates, the improvement which comprises etching each oscillator plate to a thickness beyond that required to increase its frequency to a predetermined value, bombarding the etched plate with high speed deuterons adapted to decrease its frequency of oscillation, and terminating the treatment of the etched plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value.

11. In the manufacture of quartz oscillator plates that have been stabilized by baking, acid' washing or other treatment and that have a frequency of oscillation higher than desired, the improvement which comprises bombardingeach stabilized oscillator plate with high speed deuterons adapted to decrease its frequency of oscillation, andterminating the treatment of the stabilized plate with said high speed deuterons when its frequency of oscillation reaches a predetermined value.

12. In the manufacture of quartz oscillator plates, the improvement which comprises treating each plate to the action of high speed deuterons adapted to decrease its frequency of oscillation, treating the plate to the action of ultraviolet light rays adapted to increase its frequency of oscillation, and terminating th treatment of the plate with the ultra-violet rays when its frequency of oscillation reaches a predetermined value.

13. In the manufacture of quartz oscillator plates, the improvement which comprises heating each plate to an elevated temperature to sensitize it to frequency change, treating each sensitized plate to high speed deuterons adapted to decrease its frequency of oscillation, and terminating the treatment of each plate with said high speed deuterons when its frequency of termination reaches a predetermined value.

14. In the manufacture of quartz oscillator .plates, the improvement which comprises heating each plate to an elevated temperature to sensitize it to frequency change, treating each sensitized plate to the action of high speed deuterons adapted to decrease its frequency of oscillation, treating the plate to the action of ultraviolet light rays adapted to increase its frequency of oscillation, and terminating the treatment of the plate with said ultra-violet light rays when its frequency of oscillation reaches a predetermined value.

15. In the manufacture of quartz oscillator plates, the improvement which comprises heating each plate to an elevated temperature to sensitize it to frequency change, treating each sensitized plate to the action of high speed deuterons adapted to decrease its frequency of oscillation, heating the plate so treated to increase its frequency of oscillation, and terminating the heating of the plate when its frequency of oscillation reaches a predetermined value.

16. In the manufacture of oscillator plates the step comprising decreasing the frequency of the oscillator plate by bombarding the same with high speed deuterons.

CLIFFORD FRONDEL. 

